2013/14年流行期に患者より分離されたインフルエンザA/H1N1pdm09, A/H3N2，Bウイルスのノイラミニダーゼ遺伝子と薬剤感受性との関連についての検討2013/14年流行期に患者より分離されたインフルエンザA/H1N1pdm09, A/H3N2，Bウイルスのノイラミニダーゼ遺伝子と薬剤感受性との関連についての検討AN00215478Analysis of the Neuraminidase Amino Acid Sequences of Influenza A/H1N1pdm09, A/H3N2, and B Viruses Isolated from Influenza Patients in the 2013/14 Japanese Influenza Season

Background : Neuraminidase (NA) is an essential surface protein for influenza virus replication. NA inhibitors are commonly used for the treatment of influenza patients in Japan. Several mutations that reduce the effect of NA inhibitors have been reported. We sequenced the whole NA segment of isolated virus from influenza patients and investigated the relation between the NA amino acid sequence and the 50% inhibitory concentration (IC_<50>) of four NA inhibitors.Materials and Methods : A total of 20 viruses that showed high or low IC_<50> of NA inhibitors were selected from A/H1N1pdm09, A/H3N2, and B isolates from the viruses isolated from patients in the 2013-14 influenza season. Viral RNA was extracted and RT-PCR was done. The amplified genome was sequenced using a “next generation sequencer”, and the deduced amino acid sequences were analyzed.Results : Two A/H1N1pdm09 viruses that showed very high IC_<50> for oseltamivir (150nM and130nM) contained the H275Y mutation. Otherwise, no significant relation was found between the NA amino acids and the IC_<50> of the four NA inhibitors. There was no significant relation between the NA amino acids and the IC_<50> of the four NA inhibitors for A/H3N2 viruses. The B viruses that showed a high IC_<50> for oseltamivir and laninamivir shared some amino acids. The B viruses that showed a high IC_<50> of zanamivir and peramivir also shared some amino acids. They were different from the shared amino acids found for oseltamivir and laninamivir.Conclusion : The previously reportedH275 Y mutation that causes oseltamivir resistance was found in the two A/H1N1pdm09 viruses that showed a very high IC_<50> for oseltamivir. No additional NA amino acid sequences related to the IC_<50> of the four NA inhibitors was found. The meaning of the shared amino acids among B viruses that showed a high IC_<50> would be an interesting target for further investigation.